The exemplary embodiment relates to the digital imaging arts. It finds particular application in conjunction with a method and apparatus for utilizing marks which simulate natural defects for embedding information in hard copy documents and may be used to distinguish authentic hardcopy documents from counterfeit documents.
Machine readable information in the form of watermarks, barcodes, and the like has been embedded into images on paper for a variety of applications, such as document identification and authenticity verification. The code is generally invisible or visually unobtrusive and may be decoded by a device which is capable of reading the information. Current counterfeit prevention systems are frequently based on the use of digital watermarks. Digital watermarking is a technique which allows a user to add information (e.g., copyright notices, security codes, identification data, etc.) to digital image signals and documents. Such data can be in a group of bits describing information pertaining to the signal or to the author of the signal (e.g., name, place, etc.). Most common watermarking methods for images work in spatial or frequency domains. However, such techniques, while suitable for digital documents, are often not sufficiently robust to allow detection of the marks in hardcopies, i.e., when the digital document is rendered in physical form.
There remains a need for alternative systems and methods to provide watermarking techniques for identification of images and/or documents, for uses such as prevention of counterfeiting.